Electric field driven phase transition and possible twining quasi-tetragonal phase in compressively strained BiFeO3 thin films

Highly compressively strained BiFeO3 thin films with different thickness are epitaxially grown on （001） LaA103 substrates and characterized using various techniques. The quasi-tetragonal phase with a giant axial ratio of -1.25 and its thickness-dependent evolution are investigated. An inter- esting twining structure of the quasi-tetragonal phase is evidenced in thicker films through detailed reciprocal space mapping, which becomes more pronounced with increasing film thickness. More- over, an interesting electric-field driven phase transition was evidenced in the film with a thickness of 38 nm, in which the quasi-tetragonal and rhombohedral phases are close to each other in energy landscape.